1. Technical Field
The present invention relates to an electro-optical apparatus and electronic equipment.
2. Related Art
In electronic equipment with a display function, transmissive type electro-optical apparatuses and reflective type electro-optical apparatuses are used. These electro-optical apparatuses is irradiated with light and the transmitted light or the reflected light which is modulated by the electro-optical apparatus forms a display image, or is projected onto a screen to form a projected image. Liquid crystal apparatuses are known as the electro-optical apparatuses which are used in this kind of electronic equipment and these apparatuses form images using the dielectric anisotropy of the liquid crystal and the optical rotation property of light in the liquid crystal layer. An element substrate and a counter substrate are used in the liquid crystal apparatuses, scanning lines and signal lines are arranged on the element substrate which corresponds to an image display region, and pixels are arranged in the form of a matrix at the intersections thereof. Pixel transistors are provided in the pixels and an image signal is supplied to a pixel electrode of each of the pixels via the pixel transistor as a pixel potential. On the other hand, a common electrode is provided on the counter substrate and an image is formed according to the potential difference between the common electrode and the pixel electrodes.
In order to decrease the driving voltage in the liquid crystal apparatus, common potential inversion driving which sets the common potential which is supplied to the common electrode to an alternating potential is known. In general, the cycle of the common potential inversion driving is set to a frame period. On the other hand, polarity inversion driving is necessary in order to preserve the durability of the liquid crystal material in the liquid crystal apparatus. In polarity inversion driving, frame inversion driving which inverts the polarity for every frame, 1H inversion driving which inverts the polarity for every horizontal scanning period, dot inversion driving which inverts the polarity for every pixel, and the like, are known. When common potential inversion driving and 1H inversion driving, or common potential inversion driving and dot inversion driving are executed at the same time, since the pixel potential changes in the capacitive coupling along with the changes in the common potential, the driving voltage is actually increased rather than being decreased. For example, JP-A-2010-102151 describes a method for solving this problem. In JP-A-2010-102151, the common potential is changed after resetting the pixel potential and the common potential to the same potential.
In addition, region scanning is known as a driving method for a liquid crystal apparatus. As shown in JP-A-2004-177930, region scanning is a driving method where a plurality of sub-field regions are used in order to display one image (an image of one frame) and the sub-field regions move inside the display region. When this driving method is used, time-split gradation expression and the like are possible for polarity inversion driving and digital driving.
However, in the electro-optical apparatus which is described in JP-A-2010-102151, since the pixel potential and the common potential are the same potential, although for a short period, the contrast ratio is decreased and there are difficulties in practical use. In addition, even with a combination of region scanning and common potential inversion driving, decreasing the driving voltage (lowering the voltage) is difficult for the same reasons as above, that is, the capacitive coupling. In other words, there is a problem in the electro-optical apparatuses of the related art in that it is difficult to achieve both lower voltage and improved durability, both lower voltage and region scanning, or the like. Furthermore, there is a problem in the electro-optical apparatuses of the related art in that displaying high quality images with excellent uniformity in a display region is difficult.